The invention relates to an actuator and to a liquid ring machine for fluid and especially to a liquid ring machine which comprises a rotor means, such as a blade wheel, which is eccentrically rotatable relative to the casing and provides a positive transfer of fluid. The invention relates also to a method for an actuator and especially to a method for positive transfer of fluid
The skilled person is aware of various actuators, such as eg. liquid ring pumps, which are commonly used in applications relating to the transfer of fluid or pumping, such as in the processes and apparatus of the chemical industry, papermaking industry or food industry or in the pumping operations of power plants, waste water plants or similar. The known liquid ring pumps usually comprise a stationary casing and a blade wheel or rotor which is eccentrically rotatable thereto. The blade wheel is rotated by an external motor, usually by an electric machine. Annexed FIGS. 1a and 1b are referred to in view of the prior art.
This about 60 years ago presented liquid ring pump has achieved a great popularity, especially because of the relatively simple construction thereof and the high reliability in use. The disadvantage of the solution has however been the poor efficiency (about 40%) thereof and the poor adjustability. The poor efficiency is mainly a result of the fact that when the blade wheel rotates the liquid ring, about a half of the power of the drive motor is consumed to overcome the friction between the ring and the inner surface (inner periphery) of the casing. In addition, this causes erosion in the casing and an uneven flow and splattering. The friction work causes also a heating of the pump and also a heating of the liquid to be pumped.
It is an object of the present invention to overcome the disadvantages of the prior art and to provide a new solution for an actuator, such as a liquid ring pump, and a method for using an actuator, such as for a positive fluid transfer. The solution according to the invention provides for instance a liquid pump which has an efficiency which is essentially improved relative to the known solutions.
An object of the invention is also to provide a liquid ring pump and a method for transferring fluid, by means of which a better adjustability than in known solution is achieved.
An object of the invention is to provide a solution, by means of which the size of the drive motor of a rotatable actuator, such as a blade wheel means, feed screw etc., can be reduced.
An object of the invention is to provide a solution, by means of which the heating of the machine and the heating of the fluid to be transferred can be reduced.
An object of the invention is a solution which provides an integrated electric machine-gearing actuator.
The invention is based on the idea that the casing part of a liquid ring machine, planetary gear, feed screw structure etc. is arranged to be rotatable. The casing part may preferably be arranged so as to form a hollow rotor means of an electric machine which is rotated in a desired manner relative to the actual, inside the casing provided blade wheel or similar rotatable part. This inventive idea is facilitated by a realization of the fact that in an electric machine the electric flux penetrates only to the surface layer of the rotor, the core part of the rotor having only a small influence to the operation of the machine.
More precisely, the actuator according to the present invention, such as the liquid ring machine, is mainly characterized by what is disclosed in the appended claims.
According to one preferred embodiment the actuator, such as a liquid ring machine, comprises a blade wheel means which is rotated by an external drive device and which is supported on bearings relative to the body of the machine. In addition, the apparatus comprises a rotatable casing means which is eccentrically disposed relative to the blade wheel means. The rotation of the hollow casing means is provided by an arrangement according to which the shell thereof acts as a rotor. Stator means surrounding the rotor are attached to the body of the machine. In this context a reference is made to DE 36 41 142 C2 patent publication, which in FIGS. 1 and 2 thereof discloses one example of a hollow rotor.
It is possible to provide the rotor means with various means effecting the operation thereof, such as by short circuit rings of copper or aluminium or by so called squirrel cage or coiling. Correspondingly, the stator means may eg. comprise so called formed stator teeth without departing from the scope of the invention.
The current supply arrangements, seals and bearings of the different rotating shafts can be implemented in a per se known manner, for instance the bearings can be ball or slide bearings and the seals can be box seals, and they are thus not explained on more detail.
Said rotor provided from the casing can be rotated in a same speed with the blade wheel, but the speed may also be different. The rotational speeds of these two may also be separately adjusted, whereby the difference in speeds therebetween is adjustable. This enables a good adjustability of the machine, since the number of different speeds and/or differences in speed variations becomes essentially high.
Remarkable advantages are obtained by the invention. For example, the efficiency coefficient of a liquid ring machine is remarkably improved due to an essentially remarkable decrease in the influences of friction. The rise in the temperature caused by the friction work is essentially decreased. In addition, the power requirement is decreased, and thus it is possible to use a smaller drive device for the rotation of the blade wheel, which has an essential influence in view of the purchasing and operation costs of the device. The decrease in the power requirement is estimated to be about 50%. The outer diameters of the liquid ring machine are still moderate, when considering the advantage obtained. In addition, the erosion of the inner periphery of the casing and splattering decrease essentially, or are even entirely removed. By means of the invention it is possible to provide an essentially compact structure, such as an actuator containing an electric machine and a gearing device.